stmmac: Enable unicast pause frame detect in GMAC Register 6

Unicast pause frame detect was not being enabled for the Synopsys stmmac. This
patch sets Unicast pause frame detect in MAC register 6 so that pause frame
detection by the stmmac conforms to IEEE 802.3, Annex 31B.3.3 Receive
Operation - Specifically, a MAC shall respond to pause frames containing
either the reserved multicast address or the unique physical address
associated with this station.

Signed-off-by: Vince Bridgers <vbridger@opensource.altera.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/dwmac1000_core.c

@@ -201,7 +201,10 @@ static void dwmac1000_flow_ctrl(struct mac_device_info *hw, unsigned int duplex,
 				unsigned int fc, unsigned int pause_time)
 {
 	void __iomem *ioaddr = hw->pcsr;
-	unsigned int flow = 0;
+	/* Set flow such that DZPQ in Mac Register 6 is 0,
+	 * and unicast pause detect is enabled.
+	 */
+	unsigned int flow = GMAC_FLOW_CTRL_UP;
 
 	pr_debug("GMAC Flow-Control:\n");
 	if (fc & FLOW_RX) {